1. Field of the Invention
The present invention pertains to a wall structure for a building, such as used to form a geodesic dome, and more particularly, to a composite wall structure and method wherein structural elements are interconnected to one another and into an array of triangular shaped compartments that are interiorly pressurized. Even more particularly, the invention pertains to a composite structure for the hull of a pressurized vehicle, such as an airship or submarine, wherein an array of internally pressurized compartments is connected to a fluid impervious closure skin to form a hull structure of predetermined shape and capable of captivating a volume of air and/or resisting buckling or failure resulting from fluid pressure on the hull during operation in air or water environments.
2. Description of Related Art
Interconnecting a plurality of rods, beams, struts and like structural elements to one another and forming a spherical dome is known. In general, the opposite ends of these structural elements are connected wherein to form an array of wall elements of like geometrical shape, such as a triangle and a hexagon.
By way of example, reference is drawn to U.S. Pat. No. 6,295,785, “Geodesic Dome and Method of Constructing Same” issuing Oct. 2, 2001 to the Applicant herein. The '785 Patent is specifically incorporated herein in its entirety.
In general, the geodesic dome is an almost spherical structure based on a network of struts arranged on great circles (geodesics) lying on the surface of a sphere. The geodesics intersect to form triangular elements that create local triangular rigidity and distribute the stress. The triangles create a self-bracing framework that gives structural strength while using a minimum of material. The geodesic dome is efficient, inexpensive and durable. A sphere is already efficient in that it encloses the most volume with the least surface. Thus, any dome that is a portion of a sphere has the least surface through which to lose heat or intercept potentially damaging winds.
Further, of all known structures, a geodesic dome has the highest ratio of enclosed area to weight. Geodesic domes are far stronger as units than the individual struts would suggest. The sub-pattern of triangles bulges out so that their vertices lie in the surface of a sphere and create great circles (“geodesics”) to distribute stress across the structure.
There is, however, an ongoing need for improvements in the method and structure used in constructing geodesic domes and like-shaped buildings, such as those described in U.S. Pat. No. 6,295,785. For example, a strengthened less costly polyhedral structure would be beneficial in that such structure could be used to support the downward weight of an even larger dome.
The structure of the geodesic dome must be designed to withstand dynamic forces, such as those occasioned by earth tremors and imposed by wind. A strong lightweight polyhedral structure is believed desirable in building a domed structure in an earthquake prone region, both for resisting forces arising from a vertical shock and planar earth shifting force. Typically, wind forces are applied on only one side of the dome or in one horizontal direction, not simultaneously 360° about the entire exterior of the dome. As such, the triangular elements of the polyhedral structure must ultimately be able to withstand wind forces placed anywhere on the dome.
There is reason to believe that the concept used in the construction of the geodesic dome can be effectively extended to any shape, although it works best in shapes that lack corners to concentrate stress. For example, a logical extension of the concepts employed in constructing a dome are extendable to the outer wall of a vehicle operated at a high altitude, such as a rigid lighter that air airship, or a boat operating at least in part atop the water, or operating at an extended depth below the water.
In the case of the submarine, the hull structure includes outer and inner hulls, which form a ballast tank that is fillable with water, and forms a pressurized interior compartment for personnel and equipment. The submarine can float because the weight of water that it displaces is equal to the weight of the ship. The displacement of water creates an upward force (“the buoyant force”) that acts opposite to gravity, which would pull the ship down. When the ship is on the surface, the ballast tank is filled with air and the overall density is less than that of the surrounding water. To submerge, the ballast tanks are flooded with water and air in the ballast tank vented until its overall density is greater than the surrounding water. The outer hull must resist inward forces of the body of water, which surrounds the submarine, from collapsing the hull.
Similarly, the rigid airship includes an exterior envelope and an internal skeleton that maintains the shape of the airship and defines an interior cavity for containing a pressurized lighter than air lifting gas, such as helium or hydrogen. Similar to the submarine, the airship controls its buoyancy in the air. That is, the airship displaces a volume of air of the surrounding medium whose weight is equal or greater than the total weight of the immersed body. If the weight of the body is less than the displaced air, the body has positive buoyancy (i.e., rises). As the airship ascends, the lifting gas expands due to the reduction of the ambient pressure. The exterior sheet of the airship must maintain the shape; resist overpressure inside the airship hull as the airship rises.
Whether for use at a high altitude or deep submergence, the hull must maintain the shape and integrity of the vehicle hull. Desirably, the principles applied in the constructing a geodesic dome and like structures could be applied to a vehicle operated at high altitudes and/or a great depths below the sea, wherein the hull is subjected to a continuous 360° pressure